set encoding utf8 set term svg enhanced font "Liberation-Sans" #set term postscript eps color enhanced set out "bulbs.svg" set grid sigma = 5.67e-8 sfb(x) = sigma * (x+273.15)**4 emitance=0.4 Planck(x,t) = emitance * 1e-4 * \ 1E-6*3.741E-16/(( exp(5*log((x*1E-6))) )*(exp(1.439E-2/(x*t*1E-6))-1)) abst(x)=x+273.15 set title \ "Radiation of a tungsten wire if spectral emittance was 0.4 \ - Planck functions\ \n (a band 0.45 μm to 0.65 μm is shown, \ the important one for lighting)" set ylabel \ "( λ / μm ) · \ {spectral radiant exitance} \ /(W·cm^{/*0.7 -2}μm^{/*0.7 -1})" set xlabel "ln(λ / μm)" set xrange [-1:2] #set yrange [0:2e6] set xtics 1 nomirror set x2label "λ / μm" set x2tics ("0.4" log(.4), "0.75" log(.75), "1" log(1), "2" log(2), \ "3" log(3), "4" log(4)) set arrow from log(.45), graph 0 to log(.45), graph 1 nohead set arrow from log(.65), graph 0 to log(.65), graph 1 nohead plot \ exp(x)*Planck(exp(x),2300) title '2300 K' lt 1 lw 3, \ exp(x)*Planck(exp(x),2600) title '2600 K' lt 2 lw 3 , \ exp(x)*Planck(exp(x),2900) title '2900 K' lt 3 lw 3 quit